Harvesting anchorage-dependent mammalian cells by conventional methods (i.e. protease treatment or scraping) is time consuming and may alter cell metabolism and/or membrane components. Our preliminary experiments indicate that external ultrasonic irradiation of closed culture flasks remove human diploid fibroblasts as efficiently as trypsinization, without cell death or loss of reproductive potential. We will study and develop prototypes of ultrasonic devices for harvesting mammalian cells from commonly used culture surfaces, including flasks, roller bottles, and microcarrier beads. We will determine the optimum frequencies, energy intensities, and energy exposures for each type of vessel and for several mammalian cell lines (human and mouse fibroblasts, MDCK, BHK-21, HEP-1). We will span the frequency range for 10kHz to 100kHz and the energy range from 5 to 50 mW/cm2. The most important goals would include minimal loss of cell viability and maximal retention of growth potential. Other important goals are simplicity and speed of harvest. We will determine whether sweeping frequencies ("chirping"), ultrasound pulses and/or varying wave forms would be more effective in cell removal than continuous waves. This is an innovative pilot project designed to expand an existing technology of practical importance in biomedical research. It also provides a new application of ultrasound and translates itself into a useful technology that could yield new information on the attachment of cells to their culture substrates.